Well, I sort of misread your post and thought your were capturing from you camera. That's where Image Capture comes into play. Keep that in mind, though.

For the internet images, the simplest way to do it would be to make a new folder on your desktop and simply drag/drop the images from Safari straight to that folder. No middleman (iPhoto), you'd have all of the images in one folder where you (I assume) want them.

And then from there I can use iPhoto to look at them, create a slideshow, manupulate, and maintain???